Short- and Long-Term Storage of Non-Domesticated European Mouflon (Ovis aries musimon) Cumulus-Oocyte Complexes Recovered in Field Conditions

Simple Summary: The European mouflon (Ovis aries musimon) is a non-domesticated and highly adaptable species. It is a descendant of the primitive domestic sheep (Ovis aries), with native populations inhabiting Sardinia and Corsica since the Neolithic age. In the 1950s, as a consequence of intense hunting and poaching, some animals were relocated to nearby islands (Giglio Island and others) as a conservation strategy to avoid extinction risks. Since then, this isolated way of life has served as a "time capsule" in which the Ovis aries musimon has maintained ancestral genetic traits no longer detectable in the current native Sardinian population. Our study findings report the application, in field conditions, of short- and long-term storage techniques of immature cumulus-oocyte complexes (COCs) which were then transported to the laboratory for in vitro maturation (IVM) and assessment of nuclear and cytoplasmic maturation. Both techniques mentioned above can be used for oocyte storage and in vitro culture. However, it is still necessary to optimize them, particularly when used in taxonomically related and endangered wild species for the preservation of ancestral genetic traits and to address the risk of extinction of native populations. Reproductive biotechnologies can be used as a supporting tool, through gamete conservation and in vitro embryo production, in the preservation of invaluable and irreplaceable animal genetic resources. In the present study, immature mouflon cumulus-oocyte complexes (COCs) collected from ovariectomized female ovaries underwent short- or long-term conservation (24 h maintained in Earle's/Hank's (EH) medium or vitrification) under field conditions and afterwards transported to the laboratory where they were cultured for in vitro maturation (IVM) and assessed for oocyte meiotic competence and bioenergetic-oxidative status. Utilization of both storage techniques led to COC morphology preservation, as well as cumulus expansion and oocyte meiotic resumption after the IVM procedure. Quantitative bioenergetic-oxidative parameters were reduced in vitrified oocytes compared with EH ones. Immature COC storage needs to be optimized in both domesticated and non-domesticated sheep as a part of the strategy to avoid the loss of valuable genotypes of these animal species.